This invention relates to a method and apparatus for ablating unwanted material from a patient""s vasculature, and more particularly, to rotational ablation atherectomy devices.
Vascular diseases, such as atherosclerosis and the like, have become quite prevalent in the modern day. These diseases may manifest themselves in a number of ways, often requiring different forms or methods of treatment for curing or mitigating the adverse effects of the diseases. For example, vascular diseases may take the form of deposits or growths in a patient""s vasculature which restrict, in the case of a partial occlusion, or, stop, in the case of a total occlusion, blood flow to a certain portion of the patient""s body. This can be particularly serious if, for example, such an occlusion occurs in a portion of the vasculature that supplies vital organs with blood or other necessary fluids.
To treat these diseases, a number of different therapies have been developed. For example, medical instruments have been developed that remove the material occluding a vascular lumen. Such instruments, sometimes referred to as atherectomy devices, use a variety of material removal instruments, such as rotating cutters or ablative burrs, for example, to remove the occluding material. (The term xe2x80x9catherectomy devicexe2x80x9d as used in the specification refers to a device for removing an occlusion in any portion of a patient""s vasculature. Thus, while the atherectomy devices provided in accordance with preferred embodiments of the present invention are well suited for use in the coronary arteries, their use is not limited to the coronary arteries.) In rotational atherectomy devices, the material removal instrument is typically rotated via a flexible driveshaft that is connected to an electric motor or a turbine.
In operation, a guide wire is first routed from a point on the patient""s exterior to the site of the occlusion. The material removal instrument is then advanced over the guide wire until it is positioned just proximal to the occlusion. The motor or turbine then rotates the driveshaft and the material removal instrument. As the material removal instrument is rotating, it is advanced through the occluded vessel. The material removal instrument removes the occluding material from the vessel, rather than merely displacing or reforming the material as is done in a balloon angioplasty procedure.
One example of a rotational ablation atherectomy device is the Rotablator(copyright) system, sold by Boston Scientific Corporation. This system includes an advancer housing that encloses an air-driven turbine drive assembly. A material removal instrument comprising an ablation burr coupled to a flexible driveshaft, is rotatably connected to the drive assembly. Depending on the location of the occlusion within a patient""s vasculature and other considerations, a burr of a particular shape and/or size is selected, and the driveshaft length is specified. The driveshaft is coupled to the drive assembly in the advancer housing, such that torque from the drive assembly is transmitted through the driveshaft to the burr. The burr is advanced and retracted through the occlusion via longitudinal motion of the drive assembly.
In current embodiments of the Rotablator(copyright) system, the driveshaft is coupled to the drive assembly, by a thin connector tube that is attached to a proximal end of the driveshaft. The connector tube must be axially aligned with and connected to a second thin connector tube extending distally from the drive assembly. The connector tubes are interlocked and held in place with a tubular sheath that slides over the interlocked joint. Such a connection is sometimes referred to as a xe2x80x9chandshakexe2x80x9d connection. The driveshaft and drive assembly tubes are narrow, having a diameter of approximately 1 millimeter. It may be difficult therefore to align and interlock the connector tubes even under optimal conditions. When performing an atherectomy procedure, however, the cardiologist or other operator of the device wears surgical attire and a stiff shield to protect against x-rays, making it more difficult for the operator to perform the precise movements needed to couple a conventional handshake connection.
Given the considerations discussed above, it is desirable to provide a rotational ablation atherectomy device in which it is easier to couple the drive assembly to the driveshaft. The present invention fulfills this need, and provides further related advantages.
Briefly, the present invention provides an improved ablation assembly that is easier to use. In a preferred embodiment, a drive assembly is positioned within a housing, and is slidably movable along a longitudinal axis of the housing. A hollow shaft is coupled to a prime mover in the drive assembly, such as an electric motor or turbine, and extends towards a distal end of the housing. An elastomeric plug is positioned in the drive assembly, and a longitudinal aperture extends through the elastomeric plug in axial alignment with the shaft. An ablation instrument, such as a rotatable burr, is coupled to a distal end of a flexible driveshaft. A connector tube is coupled to a proximal end of the driveshaft, the tube being adapted to connect the driveshaft to the drive assembly.
In order to assist the operator in grasping and manipulating the driveshaft and associated connector tube, a catheter-body connector slidably engages the driveshaft adjacent the proximal end, such that the driveshaft extends longitudinally through the catheter. The connector tube is inserted into the drive assembly shaft until a proximal end of the connector tube is pushed into the aperture of the elastomeric plug. An interference fit is created between the connector tube and the elastomeric plug, thereby coupling the driveshaft to the drive assembly.
Although the elastomeric plug may be positioned in various locations in the drive assembly, in a preferred embodiment, it is provided in an aperture extending axially from the prime mover. In order to facilitate insertion of the connector tube into the shaft, a proximal end of the tube is tapered or formed as a smooth ball on the end of the tube. Also, in a preferred embodiment, a stop is provided on the connector tube that abuts a distal end of the shaft when the connector tube is engaged by the elastomeric plug.
In this manner, the driveshaft is easily coupled to the drive assembly by simply pushing the proximal end of the connector tube into the shaft extending through the housing. The connector tube coupled to the proximal end of the driveshaft extends through the length of the shaft and into the elastomeric plug. If it is desired to remove the ablation instrument from the advancer housing, the catheter-body connector is disconnected and the tube is pulled away from the housing, thereby disengaging the driveshaft tube from the elastomeric plug.